CORROSION PREVENTION DURING ACID CLEANING IN DIGESTERS AND EVAPORATORS

摘要

In the United States of America, Kraft digesters and evaporators are typically acid cleaned to remove scales that precipitate from chemical species present in liquors. Though the presence of such scales is not harmful from the corrosion point of view, their removal may affect the base metal where they grow on. Scale removal may in turn affect the condition and integrity of the equipment by causing general or localized corrosion, which can lead to unexpected failures. The objective of this work was to determine optimal cleaning practices for Kraft digesters, evaporators and other equipment during scheduled shut downs to minimize cleaning costs, maximize its effectiveness during cleaning and to ultimately minimize corrosion (metal loss) during scale removal. This article presents results from a laboratory study dedicated to study the variables obtained in a nation wide survey.